Incident Overview
During the takeoff roll, the pilot radioed that a door had popped open and that he needed to return to the airport. A witness who was also a pilot observed the aircraft climb above treetop level before it began to lose altitude. Another witness reported that the aircraft leveled off and then started to sink, after which the nose came up again, but the aircraft settled back to the ground and rolled off an embankment.
Sequence of Events
After going over the embankment, the aircraft became airborne again and impacted in a nose-down attitude. A ground witness near the runway recalled that when the aircraft passed his position, the door was open and an object that looked like a seat belt was hanging out of the top of the door.
Examination Findings
An examination of the door revealed no preimpact problem that would have prevented it from closing properly. Impact marks were found on the ground near the end of the runway where the landing gear had touched down hard before the aircraft went over the embankment.
Operational Considerations
According to the operator's manual, an unlocked door would not affect the flight characteristics, except to slightly reduce the climb rate.